I was under the impression that a smoothbore has more velocity,with a ball,than a rifled bore bacause of less friction. In the thompson center book it gives the following velocitys,with 100 grains ffg .54 1855,.56 1300,.58 1428.I can understand the .54 being the fastest,lighter ball,but why is the .56 the slowest ? I need typing lessons
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I've wondered the same thing and the main possibilities I can think of are:
1) It's a typo (doubt that)
2) There's more friction in the smoothbore as it's rubbing the bore walls with it's full circumference, instead of only being in contact with the half dozen lands of a rifled barrel.
1) It's a typo (doubt that)
2) There's more friction in the smoothbore as it's rubbing the bore walls with it's full circumference, instead of only being in contact with the half dozen lands of a rifled barrel.
Leonredbeard
54 Cal.
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I have said this before and, sadly, have not had access to chronograph to porve it. Friction cause the load to start moving more slowly which causes the powder to burn more efficiently which raises the pressure which results in higher velocities.
YHWH bless.
volatpluvia
YHWH bless.
volatpluvia
This discussion comes round every now and then. I'm pretty sure that the increased time in barrel of the rifled projectile, generates more pressure behind the ball than that generated in a smoothbore of a similar diameter. I don't think this phenomena would be as evident if black powder burned faster. Try this experiment at home... Shoot a pea from a straw. Next, shoot the same pea, but this time put your finger over the end of the straw until you are just about reach maximal, but exual, pressure. Then remove your finger. I think that the ball is exposed to a greater inital pressure in a rifled bore before it begins its 'flight' down the bore, thus achieving a greater final velocity. How else do you explain that balls fly faster from fowled barrels? What do you think?
Taylor in Texas
Taylor in Texas
Greater resistance to forward motion caused by the rifling. Then the pressure builds up and boom, greater initial velocity due to increased initial pressure. How else do you explain the fact that fowled barels shoot balls at higher velocity? The only other idea I could think up to explain this phenomena, would be that somehow fowling increases velocity through increased pressure due to fowling around the ball, creating a better gas seal around the ball, instead of increased resistance working against the ball. The second theory doesn't sit well with me and I think its hogwash. But the first theory doesn't sit perfectly well either. I keep remembering the pool balls in physics lab... :hmm: The solution has to lie with increased pressure. Thats the only way to increase the velocity, and initial pressure is the only way to generate inital motion on the ball, thus leading to increased final velocity. This shouldn't be this hard to solve, its not rocket science. :rotf:
Taylor in Texas
Taylor in Texas
:hmm: :hmm:..not sure I'm ready to buy that yet...it seems to me that:texan said:
A patched ball in a rifle is sitting on top of the 'lands' making contact in only a half dozen tiny spots...minimal friction points.
By contrast, a patched ball in a smoothbore is wedged into the bore 'wall-to-wall' and has 100% contact resistance with the bore completely around it's circumference.
If friction resistance is claimed to be the issue creating this pressure buildup and then sudden high velocity movement, the smoothbore would have far more friction from all the extra contact area.
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Or, if the claim is not a contact friction issue after all, but rather a claim that resistance is caused by the twist of the rifling, I'm puzzled how it would do that.
A ball is not expanded down into the grooves of the rifling, so it doesn't grip the grooves and get resistance from that...a patched ball simply sits up on top of the lands and rides them downbore like a train on tracks...ie: every ball I've recovered from deer or jugs of water doing penetration tests have had smooth surfaces, no rifling marks.
in the thompson center book it lists 120 grs.max load for .54 and .58,but 100 grain max for .56 why?I think roundball is right about the smoothbore having more friction causing higher pressure thus the reduced max load.On the other hand if there is more pressure why not more velocity?
rudy parnell
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All things being equal...I think that the rifle gives the spin...and the spin accounts for the increased speed. I think they call it ballistics?
I think the increased resistance is caused by the force needed to begin rotating the ball as it moves forward down the barrel. I know that the ball doesn't make contact with the lands because of the patch, but the patch does come into increased contact area in a rifle (not less) vs the contact area of a smoothbore. This is because the patch is not only contacting the faces of the lands, but also the faces of the groves and the insides of the lands, thus doubling the contact surface area of patch to rifle bore wall vs just the surface of the inside of the smoothbore. Thus increased initial pressure is required to start the rifled ball, leading to increased velocity and more powder burned behind the ball. Again I'm no rocket scientist, but I don't think rotaional velocity has the potential to increase forward velocity. Just the stability of the projectile.
Taylor in Texas
PS No one has tried to explain why fouled barrels shoot faster...
Taylor in Texas
PS No one has tried to explain why fouled barrels shoot faster...
Fouled barrels would be faster because the bore is smaller in diameter because of the fouling, therefore creating more pressure and thus more velocity. Just my pea barained thoughts. :grin: And besides, you asked. :thumbsup:
texan said:
:hmm: I'm having trouble thinking that patch cloth essentially laying loose in the grooves would dramatically increase resistance;
And so far this discussion has been based upon increased resistance required to OVERCOME INERTIA before the ball starts moving...hard to see where rifling comes in to play at that point.
:hmm:
OK...decided to go straight to the horse's mouth, since this discussion started with a reference to the TC .56cal SB.
Just hung up the phone with "Frank" in TC's repair department...I explained the discussion we were having and he didn't even hesitate...said a rifle is faster because of the rifling...said the spin of the rifling actually adds to / increases the velocity over a comparable smoothbore.
I can only assume that he knows what he's talking about.
Just hung up the phone with "Frank" in TC's repair department...I explained the discussion we were having and he didn't even hesitate...said a rifle is faster because of the rifling...said the spin of the rifling actually adds to / increases the velocity over a comparable smoothbore.
I can only assume that he knows what he's talking about.
Why not is a smoothbore? They foul too, and as the fouling builds up the bore diameter decreases, which would increase the pressure. Right, wrong, or am i out in left field here?
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